The present invention relates to a technique for improving a gas injector used in a focused ion beam apparatus.
There are a variety of applications of focused ion beam apparatuses including acquisition of a microscopic image of a sample which is carried out by scanning an ion beam on the sample to detect secondary charged particles emitted from a surface of the sample, analysis based on components thus detected, a sputter etching process utilizing irradiation with ion beams, and a deposition process in which a deposition layer is formed on a surface by irradiating to the surface with ion beams while spraying a material gas on the same. Referring particularly to focused ion beam processes, ion beams are radiated to a surface of a sample while spraying a gas on the same not only in deposition processes but also in etching processes such as gas-assisted etching.
FIG. 4 shows a major configuration of a focused ion beam apparatus for performing such an ion beam process. An ion beam 2 focused through an ion optical system 3 is appropriately deflected by a deflector 4 to irradiate a surface of a sample 9 placed on a sample stage 7. When the ion beam 2 irradiates the sample surface, secondary charged particles are driven out from the sample surface, and said secondary charged particles depend on a sample substance located in the region irradiated with the ion beam 2. The secondary charged particles driven out as a result of the irradiation with an ion beam are captured by a detector 5 which detects the amount of the charged particles of interest. The value is digitized by an A-D converter and stored in a storage section of a computer 10 as data of the region irradiated with the beam. When the computer 10 designates a predetermined region to be scanned by a beam, a deflection voltage is applied to said deflector 4 through a driving system such that the ion beam 2 is scanned in said region. A scan image of the region designated by a computer 8 is obtained when a detected value of secondary charged particles at each beam spot is stored along with position information based on such a scan, and the image can be displayed on a display 11 as needed. An operation of etching a patterned film is performed through application of an appropriate deflection voltage to said deflector 4 by the computer 10 through a driving system to irradiate the region to be processed with an ion beam based on setting from an input operation section 12. Referring to a process of forming a patterned film on a substrate, the computer 10 sprays a vapor of an organic compound or the like on a predetermined region to be patterned with a gas injector 6 through a driving system based on setting from the input operation section 12 and applies an appropriate deflection voltage to said deflector 4 through a driving system to process said region by irradiating the same with an ion beam 2.
Referring to a basic configuration of the focused ion beam apparatus, the gas injector 6 and the secondary charged particle detector 5 are provided in the vicinity of a region which is irradiated with an ion beam 2. It is not essential to provide only one gas injector, and a plurality of gas injectors may be provided for processes which require an assist gas for etching, a material gas for forming a protective film, or a material gas for forming a coating layer or conductive path. When plural kinds of gasses are used, however, the gasses may stick to and remain on inner walls when a single nozzle and a single path are used to spray the gas and may be mixed with gas components previously used when the gas types are switched, which can cancel the effects of the gasses (etching and deposition). It is therefore necessary to provide plural kinds of nozzles and paths to use plural kinds of gasses. In conventional modes, (1) a plurality of gas injectors are separately provided as shown in FIG. 3A; (2) a plurality of nozzles are combined and driven together as shown in FIG. 3B; or (3) nozzles are arranged in a row and driven together as shown in FIG. 3C. The mode (1) in which gas injectors are treated separately has a space-related problem in that a great space is occupied and, in the modes (2) and (3) in which there is a plurality of gas injector nozzles, the bundle of nozzles becomes too thick, which not only makes it difficult to move the bundle down for use and to move it up for a rest but also makes it impossible to properly move the nozzles toward a beam-irradiated position on a sample. Further, since the distance between the irradiated position and the nozzle position is different from nozzle to nozzle, it is difficult to perform adjustments such as a gas flow amount adjustment for allowing the gasses to demonstrate their effects.
Further, when a sample is irradiated with charged ion beams, a charging phenomenon or so-called charge-up occurs as the irradiation time elapses. Since such a charging phenomenon on a sample surface can affect the emission of secondary charged particles and control of an ion-beam-irradiated position, it is an important problem in the focused ion beam apparatus to prevent such charging. A frequently used means for preventing such charging is to provide an electron injector in the vicinity of a region which is irradiated with an ion beam to neutralize the same through the application of an electron shower. As thus described, the neighborhood of an irradiated region is over-populated by members to be provided, and it is a problem in designing how to adopt and provide them.
It is an object of the invention to provide a gas injector in which a nozzle end section does not become too thick even if a plurality of nozzles are used to allow the nozzles to be smoothly moved down for use and moved up for a rest and to allow the nozzles to properly approach a beam-irradiated position on a sample and in which it is possible to overcome difficulties in a gas flow amount adjustment attributable to the distance between the irradiated position and nozzle position that is different from nozzle to nozzle.
In a gas injector according to the invention, a forward section of the same is formed by a cylindrical portion which collectively contains and holds a plurality of nozzles and gas supply pipes and a nozzle guide portion which has an opening of a size to allow only one of the nozzles to protrude outwardly at an end thereof and which is formed like a taper extending from said cylindrical portion to said opening, and a rear section of the gas injector has a mechanism capable of selectively driving said plurality of nozzles for elevation through said gas supply pipes.